Rolls of strips of elastomers are known and widely used for a variety of applications. The current invention relates to a roll of elastomer strip that is reinforced with steel cords. Such a composite combines the best of two worlds: the favourable properties of toughness, impermeability, ease of processing, relative chemical inertness of the elastomer with the strength, flexibility, high-temperature resistance of steel cord. The favourable properties are further enhanced when both components adhere very well to one another. Elastomer strips reinforced with steel cord are used already many years in the form of steel cord reinforced conveyor belts, or as power transmission belts, or as intermediate products in the production of tires. More recently, such steel cord reinforced elastomer strips are gaining importance as elevator hoisting elements (WO 00/37738). In all these dynamic applications the flexibility of the steel cord is important. Therefore steel cords assembled out of many individual fine filaments are used because with these filaments, the stiffness of the wires decreases considerably (the stiffness moment of a filament is proportional to the 4th power of its diameter) and the flexibility of the cord increases provided that the filaments glide over one another.
There are however a number of quasi-static applications, where the flexibility of the steel cord is only needed for processing reasons: after the strip has been put into place, the steel cord is only statically or quasi-statically loaded and the flexibility property of the steel cord is not longer of use. The reinforcement of flexible pipes (WO 02/090812) and the repair of concrete pillars by retrofitting them with strip are non-exhaustive examples of such applications. In these applications, a roll of steel cord reinforced elastomer strip is wrapped around the object to be reinforced, being the inner pipe in case of a flexible pipe or the pillar in case of concrete repair. While the flexibility of the steel cord is needed in order to apply the strip to these objects, it is not longer needed once the strip is in place. However, introducing such flexibility into a steel cord makes the steel cord expensive: wires have to be drawn to a finer diameter and more wires have to be assembled together. A lot of effort and money is therefore put into a steel cord property that is only used once.
On the other hand, when stiffer steel cords are used in order to lower the cost, the bending around the article to be reinforced introduces residual stresses in the strip and makes the application of the strip onto the object to be reinforced much more difficult. This leads to a stress imbalance in the reinforcing layer. Also these residual stresses can be dangerous because the strip can spring back when the end is loosened. In addition the larger stiffness makes the attachment of the start or end of the strip more difficult. The increased stiffness of the strip also increases the forces on the object that is wrapped by the strip. In the case of repair of concrete pillars, this is not too much of a problem, but in the case of flexible pipes, the inner pipe must be made strong enough in order not to collapse under the force exerted by the strip during winding. I.e. the stiffness of the strip would inhibit the use of thin walled inner pipes.